Control unit for adjusting the angle of rotation of a camshaft

ABSTRACT

The present invention relates to a control unit for adjusting the angle of rotation of a camshaft in relation to the angle of rotation of a crankshaft in internal combustion engines in order to influence the control times, whereby a wobble plate mechanism which realizes the adjustment is arranged between camshaft and crankshaft, preferably between camshaft and camshaft wheel.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a control unit for adjusting theangle of rotation of a camshaft in relation to the angle of rotation ofa crankshaft, as is known from DE 41 35 378 for example.

[0002] In internal combustion engines, the crankshaft drives one or morecamshafts via a primary drive, which is realized as a chain, toothedbelt, upright shaft or as a series of gear wheels. To do this, acamshaft wheel, via which the primary drive drives the camshaft, isfixed to each camshaft and is realized corresponding to the primarydrive as a pulley wheel or sprocket wheel, for example. This alwaysinvolves a gear ratio reduction of the angular rotation of thecrankshaft, in which 720° angular rotation of the crankshaft isconverted into 360° angular rotation of the camshaft.

[0003] In order to ensure that the working cycle of the internalcombustion engine runs precisely, and to maintain the control timesrequired for exact combustion, the crankshaft, primary drive andcamshaft are manufactured to very tight tolerances.

[0004] In this, it is advantageous to eliminate the fixed relationbetween the crankshaft and the camshaft, for example for speed-dependentadaptation of the control times of the valve lash, and to allow thecamshaft to lead or lag the crankshaft. This is achieved in a simplemanner by means of a control unit which displaces the camshaft inrelation to the camshaft wheel. The combustion chambers of the internalcombustion engine are opened and closed correspondingly earlier or laterby the valves as the camshaft turns during the working cycle. Thisprovides an opportunity of further improving the running characteristicsof the internal combustion engine so as to save fuel and, above all, toreduce exhaust emissions.

[0005] Such a control unit is known from the generic DE 41 35 378. Herethe camshaft of an internal combustion engine is displaced in relationto the crankshaft by means of a hydraulic control unit. The hydrauliccontrol unit includes a wobble plate pump which provides the hydraulicpressure required to displace the camshaft.

[0006] The disadvantages of a hydraulic control unit lie in theextensive space occupied by the pump arrangement and the hydraulicchamber system, the arrangement's susceptibility to faults, and therelatively high manufacturing costs.

SUMMARY OF THE INVENTION

[0007] The object of the invention is to provide a control unit foradjusting the angle of rotation of the camshaft in relation to the angleof rotation of the crankshaft, which requires little space, isinexpensive to manufacture, and which is very safe in operation.

[0008] This task is solved in accordance with the invention by thefeature described in the characterizing clause of patent claim 1, inwhich a wobble plate mechanism which effects the adjustment is arrangedbetween the camshaft and the crankshaft.

[0009] In this case, with an internal combustion engine, camshaft andcrankshaft are connected to each other via a primary drive, in which theprimary drive drives the camshaft via a camshaft wheel connected to thecamshaft. Here, the wobble plate mechanism is arranged between thecamshaft wheel and the camshaft.

[0010] A wobble plate is attached to one side of the wobble platemechanism, an actuator which drives the wobble plate is also arranged onthis side.

[0011] A further development of the invention provides for the wobbleplate on the opposite side to the actuator to have two rotating gearrings. Here, the first gear ring of the wobble plate engages in a gearring acting on the camshaft wheel, and the second gear ring of thewobble plate engages in a gear ring acting on the camshaft,

[0012] An alternative development of the invention provides for arotating gear ring to be arranged on each side of the wobble plate.Whereby the gear ring on one side of the wobble plate engages with agear ring acting on the camshaft wheel. The gear ring formed on theother side of the wobble plate engages with a gear ring acting on thecamshaft.

[0013] The displacement of the angle of rotation of the camshaft inrelation to the camshaft wheel results from the intermeshing gear ringsof the wobble plate and of the camshaft wheel and/or the intermeshinggear rings of the wobble plate and of the camshaft having differentnumbers of teeth.

[0014] Whereby the wobble plate has an axial angle in relation to thecamshaft. The effect of this is that only an angular segment of the gearrings of the wobble plate engages with the gear rings of the camshaftand the camshaft wheel. The size of the angular segment within which thegear rings intermesh is a function of the axial angle of the wobbleplate in relation to the camshaft.

[0015] A particularly simple embodiment of the invention provides forthe actuator to directly drive the wobble plate bearing the gear rings.

[0016] An alternative, somewhat more complex, embodiment of theinvention provides for the actuator to directly drive a further wobbleplate, and the further wobble plate transmits the wobbling motion viaconnecting rods in sliding bearings to the wobble plate bearing the gearrings.

[0017] Means are provided which limit the displacement of the camshaftin relation to the crankshaft to a maximum displacement of the camshaftof ±40 degrees.

[0018] In a final development of the invention, means are provided whichrealize a displacement of the camshaft in relation to the crankshaft of0 degrees if the actuator fails.

[0019] The control unit for adjusting the angle of rotation of thecamshaft in relation to the angle of rotation of the crankshaftaccording to the invention is described and explained in the followingwith the aid of four different embodiments and four figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] They show:

[0021]FIG. 1 a sectional drawing through a simply designed control unitrealized as a wobble plate mechanism, in which both gear rings arearranged on one side of the wobble plate,

[0022]FIG. 2 a sectional drawing of an alternative embodiment of thecontrol unit realized as a wobble plate mechanism, in which a gear ringis arranged on each side of the wobble plate,

[0023]FIG. 3 a sectional drawing of a further alternative embodiment ofthe control unit realized as a wobble plate mechanism,

[0024]FIG. 4 the sectional drawing through an alternative embodiment ofthe control unit realized as a wobble plate mechanism for displacing thecamshaft in relation to the camshaft wheel.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0025] The principle of operation of a simple wobble plate mechanism isbased upon a wobble plate arranged on the drive shaft of an actuatingunit, which wobble plate is at an axial angle to this drive shaft andwhich is arranged on the drive shaft such that it can rotate.

[0026] Whereby the wobble plate preferably has two gear rings, each ofwhich engages in a gear ring of a shaft (or a wheel), which thus formstwo pairs of gear rings which are meshed with each other. The axialangle ensures that only the teeth of an angular segment of the pairs ofgear rings mesh with each other. The size of the angular segment withinwhich the pairs of gear rings are intermeshed is a function of the axialangle of the wobble plate in relation to the drive shaft of theactuating unit.

[0027] The rotation of the drive shaft of the actuating unit leads towobbling rotation of the wobble plate, in which the angular segment ofthe wobble plate meshed with the shafts rotates through 360 degreesduring one wobbling revolution. The rotation of the wobble plate itselfis a function of how the shafts are driven.

[0028] In at least one of the pairs of gear rings, the two intermeshinggear rings have different numbers of teeth. This difference in thenumber of teeth leads to a displacement between the gear rings duringthe wobbling rotation of the wobble plate, in which the displacementafter one wobbling revolution of the wobble plate corresponds to theangular section taken up by the teeth forming the difference in thenumber of teeth.

[0029] For example, if the wobble plate has a gear ring of double widthwith 50 teeth which engages a first gear rings which also has 50 teeth,of a first shaft and which engages a second gear ring, which has 51teeth, of a second shaft, then one wobbling revolution of the wobbleplate leads to a displacement between the first shaft (and the actuatingunit and the drive shaft) and the second shaft of exactly one tooth(=7.2 degrees). Correspondingly, the displacement between the firstshaft and the second shaft is one full revolution after 50 wobblingrevolutions of the wobble plate, that is the gear ratio between thefirst shaft and the second shaft, and between the actuating unit of thewobble plate and the second shaft is 50:1 in the case described.

[0030] If the actuating unit of the wobble plate is at rest, thiscreates a torque on the second shaft induced by the first shaft via themeshed pairs of gear rings of the shafts and the wobble plate.

[0031] Such a wobble plate mechanism can be used very advantageously forinfluencing the control times for the valve lash of an internalcombustion engine, in which the control times are determined by theposition of the cams of a camshaft 1 which is driven, for example, via acamshaft wheel 2.

[0032]FIG. 1 shows a sectional drawing of a wobble plate mechanism whichconnects the camshaft 1 and the camshaft wheel 2, whereby the camshaftwheel 2 is connected to the crankshaft of the internal combustion enginevia a primary drive 6 designed as a timing chain.

[0033] In this very compact variant, the wobble plate 3 has a doublewidth gear ring 3.1 on the side facing the camshaft 1 and the camshaftwheel 2.

[0034] This gear ring 3.1 of the wobble plate 3 engages in a gear ring2.2 acting on the camshaft wheel 2, which gear ring is formed directlyon the camshaft wheel 2.

[0035] In addition, the gear ring 3.1 of the wobble plate 3 engages witha gear ring 1.2 acting on the camshaft 1. This gear ring 1.2 which actson the camshaft 1 is designed as a separate component 1.1, and isconnected to the camshaft 1 by means of a screw 1.3 for example. Becauseof the high friction between the gear rings with the differing numbersof teeth, in this embodiment it is advantageous to assign the outer gearring of the camshaft wheel, which has a larger area, a number of teethdifferent to that of the wobble plate.

[0036] An actuator 5 which drives the wobble plate 3, is arranged on theopposite side of the wobble plate 3 to the gear ring 3.1, said actuator5 is preferably designed as an electric motor, but it may also berealized as a hydraulic system or a mechanical drive coming from theinternal combustion engine.

[0037]FIG. 2 shows a sectional drawing of an alternative embodiment of awobble plate mechanism which connects the camshaft 1 and the camshaftwheel 2. In which, a gear ring 3.2 for connecting the gear ring 2.2 ofthe camshaft wheel 2 is formed on one side of the wobble plate 3, and agear ring 3.1 for connecting the gear ring 1.2 of the camshaft is formedon the other side of the wobble plate 3. The gear rings 1.2, 2.2, 3.1,3.2 all have the same diameter, whereby it is irrelevant which two gearrings have the different numbers of teeth. The gear ring 1.2 of thecamshaft 1 is again formed on a separately made component 1.1 which isconnected to the camshaft by screws 1.3. The camshaft 1 is equipped forthis purpose with an appropriate connecting piece for screwing on theformed part 1.1.

[0038] When the actuator 5 rotates the drive shaft 4, the wobble plate3, which has a ball bearing, executes the wobbling rotation, whereby thecamshaft 1 opposite the camshaft wheel 2 is displaced according to thegear ratio determined by the numbers of teeth on the gear rings 1.2,2.2, 3.2, 3.3.

[0039]FIG. 3 shows a further alternative embodiment of a wobble platemechanism which connects the camshaft 1 and the camshaft wheel 2, inwhich, in contrast to FIG. 2, the gear ring 2.2 of the camshaft wheel 2is designed as a separate component which is screwed onto the camshaftwheel 2 by means of screws 2.3. The separate component 1.1. of thecamshaft 1 bearing the gear ring 1.2 is connected to the camshaft 1 bythe screw 1.3.

[0040]FIG. 4 shows an alternative embodiment of a wobble plate mechanismwhich connects the camshaft 1 and the camshaft wheel 2, in which thefunctions to be fulfilled by the wobble plate are divided between afirst wobble plate 3 a and a second wobble plate 3 b.

[0041] The wobble plate 3 a is arranged on the drive shaft 4 of theactuating unit 5 and does not have any gear rings. The wobble plate 3 bthus serves to displace the camshaft 1 and the camshaft wheel 2.

[0042] The wobble plate 3 b has gear rings 3.1 and 3.2 and is floatinglymounted on a ball bearing is such a manner that the wobble plate 3 b istilted through a plurality of degrees in relation to the axis of thecamshaft without axially displacing the fictional center point of thewobble plate 3 b. The wobble plate 3 b thus serves to connect thecamshaft 1 and the camshaft wheel 2.

[0043] The rotation of the camshaft 1 would align the wobble plate 3 bbetween the gear ring 1.2 of the camshaft 1 and the gear ring 2.2 of thecamshaft wheel 2 as a result of centrifugal forces. However, the wobbleplate 3 a forces the wobble plate 3 b by means of connecting rods 3.3into the position in which the wobble plate 3 b connects the camshaft 1and the camshaft wheel 2 to one another, and in which the camshaft 1 andthe camshaft wheel 2 can be displaced in relation to each other by theactuating unit 5.

[0044] In principle, the embodiments of the invention shown in FIGS. 1to 4 enable any degree of displacement of the camshaft 1 in relation tothe camshaft wheel 2, and thus in relation to the crankshaft of theinternal combustion engine. However, a displacement of the camshaft 1 inrelation to the camshaft wheel 2 of just ±40 degrees is useful forinfluencing the control times for the valve lash of the internalcombustion engine. Thus it is useful to provide the wobble platemechanism with an arrangement which limits the displacement of thecamshaft 1 in relation to the camshaft wheel 2.

[0045] In order to precisely regulate the mainly speed-dependent,settable control times of the internal combustion engine, the camshaft 1and crankshaft of the internal combustion engine or the camshaft wheel 2are equipped with a sensor device which senses the actual position ofthe camshaft 1 in relation to the camshaft wheel 2, and transmits thesignals to a control device, assigned to the wobble plate mechanism,which regulates the actuating unit. Whereby the control device cancompare the actual and set positions of the camshaft 1 and the camshaftwheel 2 with one another, and determine appropriate correction valuesfor controlling the actuating unit if there are deviations. The sensordevice may be advantageously realized by non-contact Hall sensors.

[0046] Moreover, it is useful to provide an arrangement which ensuresthat the camshaft 1 and the camshaft wheel 2 are brought into adisplacement position of 0 degrees in relation to each other if thedrive unit 5 of the wobble plate 3 fails. The internal combustion enginethus continues to be operated without speed-dependent adaptation of thecontrol times.

[0047] The failure of the drive unit 5 can thus be detected byevaluating the sensor signals of the sensor device.

[0048] If it is not possible to bring camshaft 1 and camshaft wheel 2into a position in which they are displaced by 0 degrees in relation toeach other, fuel injection and ignition are adapted according to thedisplacement of the camshaft in order to ensure the emergency runningcharacteristics.

[0049] The control unit designed as a wobble plate mechanism fordisplacing the angle of rotation of the camshaft in relation to theangle of rotation of a crankshaft takes up little space, especially inthe embodiment shown in FIG. 1, it can be manufactured inexpensively,and has high operational safety by means of the emergency runningcharacteristics which can be realized.

What is claimed is:
 1. Control unit for adjusting the angle of rotationof a camshaft (1) in relation to the angle of rotation of a crankshaftwherein a wobble plate mechanism, which realizes the adjustment, isarranged between the camshaft (1) and the crankshaft.
 2. Control unitaccording to claim 1 wherein camshaft (1) and crankshaft are connectedto each other by a primary drive (6), in which the primary drive (6)drives the camshaft (1) via a camshaft wheel (2) which is connected tothe camshaft (1), and wherein the wobble plate mechanism is arrangedbetween the camshaft wheel (2) and the camshaft (1).
 3. Control unitaccording to claim 1 wherein a wobble plate (3) is attached to one sideof the wobble plate-mechanism, and wherein an actuator (5), which drivesthe wobble plate (3), is arranged on this side.
 4. Control unitaccording to claim 2 wherein the wobble plate (3) has two rotating gearrings (3.1,3.2) on the opposite side to the actuator (5), and whereinthe first gear ring (3.1) of the wobble plate (3) engages in a gear ring(2.2) which acts on the camshaft wheel (2), and wherein the second gearring (3.2) of the wobble plate (3) engages in a gear ring (1.2) whichacts on the camshaft (1).
 5. Control unit according to claim 2 wherein arotating gear ring (3.1,3.2) is arranged on each side of the wobbleplate (3), and wherein the gear ring (3.1) on one side of the wobbleplate (3) engages in a gear ring (2.2) which acts on the camshaft wheel(2), and wherein the gear ring (3.2) on the other side of the wobbleplate (3) engages in a gear ring (1.2) which acts on the camshaft (1).6. Control unit according to claim 4 wherein the intermeshing gear rings(2.2, 3.1) of the wobble plate (3) and of the camshaft wheel (2) and/orthe intermeshing gear rings (1.2, 3.2) of the wobble plate (3) and ofthe camshaft (1) have different numbers of teeth.
 7. Control unitaccording to claim 1 wherein the wobble plate (3) is at an axial angleto the camshaft (1), as a result of which the gear rings (3.1,3.2) ofthe wobble plate (3) only engage an angular segment of the gear rings(1.2, 2.2) of the camshaft (1) and of the camshaft wheel (2), andwherein the size of the angular segment is a function of the axial angleof the wobble plate (3) in relation to the camshaft (1).
 8. Control unitaccording to claim 5 wherein the actuator directly drives the wobbleplate (3) bearing the gear rings (3.1,3.2).
 9. Control unit according toclaim 5 wherein the actuator directly drives an additional wobble plate(3 a), and the additional wobble plate (3 a) transmits the wobblingmotion via studbolts to the wobble plate (3 b) bearing the gear rings(3.1,3.2).
 10. Control unit according to claim 1 wherein means areprovided which realize a displacement of the camshaft (1) of a maximumof ±40 degrees.
 11. Control unit according to claim 10 wherein means areprovided which realize a displacement of the camshaft (1) in relation tothe crankshaft of 0 degrees if the actuator fails.